Inkjet printers are now very common and affordable and allow one to obtain decent print quality. They are used in home printing, office printing and commercial printing. The growth of inkjet printing is the result of a number of factors including reductions in cost of inkjet printers and improvements in print resolution and overall print quality. A continued demand in inkjet printing has resulted in the need to produce images of high quality, high permanence and high durability while maintaining a reasonable cost. Inkjet printing is a popular method of non-contact printing on a broad selection of substrates.
A variety of ink types are used in inkjet printing with each type of ink having its advantages and drawbacks. Industrial inkjet printing employs primarily solvent based and UV curable inks jetted typically by piezoelectric inkjet (PIJ) print heads. Solvent inks have good adhesion and printability as well as jetting reliability and printing speed. Solvent inks, however, emit large amounts of volatile organic compounds (VOCs) considered as hazardous air pollutants (HAPS). For the use of solvent inks, installation of special VOC capturing devices and imposition of strict control on the printing site are required. Solvent inks have a low flash point and are easy flammable and therefore, must be dried at relatively low temperatures.
UV inkjet inks enable high printing speed, they have relatively good adhesion on a variety of substrates and they have low VOC content. UV inks, however, are characterized by an unpleasant odor; in addition, such inks are harmful to the environment and may cause skin or eye inflammation. The printed image from the use of UV inks possesses a small rough relief and when printed on a flexible substrate, the inks limit substrate flexibility and stretch/shrink related applications.
Aqueous (water-based) inkjet inks are used primarily in a home or an office environment. A number of commercial inkjet printers use aqueous latex inks such as, for example, HP DESIGNJET® L25500 wide format inkjet printer (Hewlett Packard, Palo Alto Calif.), which uses aqueous latex ink with thermal inkjet (TIJ) technology, and HP SCITEX® FB6700, which is flatbed PIJ printer that uses aqueous latex ink. Aqueous inks have several advantages such as, for example, low viscosity and environmentally friendliness over UV-based and solvent-based inks; the aqueous inks produce a good image quality and span the color gamut.
Drying of aqueous inks requires large amounts of energy. Moreover, as water evaporates, the ink dries in the print head nozzles. Complicated maintenance systems may be necessary to provide continued print head operation. The adhesion of aqueous inks may be limited and printing on plastic substrates has been very difficult, if not perhaps impossible.